Timer mechanism



Nov. 14, 1961 R. BERGSMA TIMER MECHANISM 4 Sheets-Sheet 1.

Filed March 25, 1957 Nov. 14, 1961 R. BERGSMA 3,009,081

TIMER MECHANISM Filed March 25, 1957 4 Sheets-Sheet 2 INVENT OR. B Z8 7" 67774 Pa e,

Nov. 14, 1961 R. BERGSMA 3,009,081 I TIMER macmmxsm Filed March 25, 1957 4 Sheets-Sheet 3 ENTOR'.

Nov. 14, 1961 R. BERGSMA TIMER MECHANISM 4 Sheets-Sheet 4 Filed March 25, 1957 United States Patent 3,009,081 TIMER MECHANISM Rudolph Bergsma, Ann Arbor, Mich, assignor to King- Seeley Thermos Co., a corporation of Michigan Filed Mar. 25, 1957, Ser. No. 648,247 18 Claims. (Cl. 317-58) The present invention relates to an improved timer mechanism, and more particularly, to an improved timer mechanism constituting an improved electric circuit con: trolling mechanism and having improved means for controlling current in an electric circuit to provide interrelated time and overload control of the current in the circuit.

It is an object of the present invention to provide an improved electric circuit controlling mechanism of the above mentioned type, which is simple in design, economical of manufacture, sturdy of construction, and reliable and efficient in operation.

It is also an object of the present invention to provide such an electric circuit controlling mechanism which includes a timer controlled main switch, an overload switch mechanism, and a reset mechanism adapted to automatically reset said overload switch mechanism at the end of the period set on said timer.

It is also an object of the present invention to provide an improved circuit controlling mechanism of the above mentioned type including main switch contacts which are timer controlled and overload contacts which are opened in response to the occurrence of a predetermined overload condition in the circuit and are automatically reset upon opening of the main switch contacts.

More specificaly, it is an object of the present invention to provide such an improved circuit controlling mechanism in which one of the main switch contacts and one of the overload contacts are movable and in which a reset element is so mounted that after movement of the movable overload contact, to open the circuit, subsequent movement of the movable main contact to its open position, positively resets the movable overload contact to its closed position.

It is a further object of the present invention to provide such an improved circuit controlling mechanism having main switch contacts which are timer controlled and overload contacts, at least one of which is movable with a snap action to a tripped or open position, and a reset mechanism which is operated by opening of the main switch contacts to reset the overload contact to its closed position with a snap action.

Another object of the present invention is to provide improved means for controlling the current in an electric circuit which includes a switch mechanism controlled by a timer mechanism having an arbor rotatable in one direction from a zero position, to move a cam element to close the switch mechanism and initiate operation of the timer mechanism to return the arbor to the zero position at the expiration of a selected interval and in which the arbor is rotatable in the opposite direction from the zero position to a position in which operation of the timer mechanism for returning the arbor to the zero position is not initiated.

Other and more detailed objects of the present invention will be appreciated by those skilled in the art from a consideration of the following specification, the appended claims, and the accompanying drawing, through out the several views of which like reference characters designate like parts, and wherein:

FIGURE 1 is an elevational view having parts broken away of a circuit controlling mechanism constructed according to the present invention;

FIGURE 2 is an enlarged sectional view of the structure 3,009,081 Patented Nov. 14, 1961 illustrated in FIGURE 1, taken substantially along the line 2-2 thereof;

FIGURE 3 is a sectional view of a portion of the switch casing illustrated in FIGURE 2, taken substantially along the line 3-3 thereof and showing the mounting of certain parts therein;

FIGURE 4 is an enlarged sectional view of the structure illustrated in FIGURE 2, taken substantially along the line 4-4 thereof;

FIGURES 5, 6, 7 and 8 are enlarged sectional views of portions of the switch casing illustrated in FIGURE 2, taken substantially along the lines 55, 66, 7-7, and 8-8 thereof, respectively, and showing the mounting of certain parts therein;

FIGURES 9, 10 and 11 are sectional views similar to FIGURE 2, showing other positions assumed by the parts of the circuit controlling mechanism at different stages during the operation thereof;

FIGURE 12 is a broken view similar to FIGURE 2 showing a modified construction;

FIGURES l3 and 14 are elevational views of certain parts of the modified construction illustrated in FIGURE 12; and,

FIGURES l5, 16, 17 and 18 are broken views similar to FIGURE 12, showing the relative positions of the parts at different stages in the operation of the modified form of circuit controlling mechanism.

Referring to the drawings, and more particularly, to FIGURE 1 thereof, the improved electric circuit contnolling mechanism of the present invention generally comprises a timer mechanism indicated at 20, having an arbor 22 provided with a knob 24 for manually rotating the arbor 22. The mechanism also includes a bell 26 which is struck to provide an audible signal at the expiration of the period for which the timer is set, and a switch mechanism housed within a switch casing 28 which is mounted on the timer 20 by means of screws 30.

The arbor 22 is rotatable by the knob 24 in one direction from a zero position to initiate operation of the timer 20, which thereupon returns the arbor 22 to its zero position at the end of the selected time interval. Timers capable of performing this function are well known and the timer 20 may be of any suitable construction, its details forming no part of the present invention.

The arbor 22 extends into the switch case 28 through an enlarged central opening 32 therein and carries a cam plate 3-4 fixed on the end thereof (for rotation therewith. In the preferred embodiment illustrated, the cam plate 34 has a hub protion 36 which rotatably supports a generally circular latch plate 38 which has an arcuately shaped slot 40 which receives a laterally projecting finger 42 integrally formed on the cam plate 3 4. The engagemerit of the finger 42 in the slot 40 provides a lost motion connection between the cam plate 34 and the latch plate 38. These plates 34 and 3-8 are provided with notches 44- and 46, respectively, which receive the follower finger 48 of a hammer 50 pivotally mounted within the timer 20, when the arbor 22 is in its zero position.

Within the switch casing 28, which is formed of a suitable insulating material, are mounted a stationary main contact 52, a movable main contact 54, a stationary overload contact 56, and a movable overload contact 58. The stationary main contact 52 is mounted in a rigid metal strip 60 which is in turn mounted in a supporting recess 62 provided in the casing 28, as best illustrated in FIGURES 2 and 5. The strip 60 extends outwardly through an opening 64 provided in the wall of the easing and its outer end portion provides a terminal 66 for connecting the circuit controlling mechanism in the electric circuit to be controlled. The movable main contact 54 is mounted near the free end of an arm 68 formed of 9 a a spring steel or other suitable electrically conductive resilient material. In the preferred embodiment illustrated, this arm 68 is secured to an anchor plate 70 supported in the casing 28, as best illustrated in FIGURE 8, where it will be seen that the anchor plate 70 extends into recess 71 provided in the casing 28.

In the preferred embodiment illustrated, the anchor plate 70 has projections 72 which extend through openings provided in the spring arm 68 and are staked over the opposite surface of the spring arm 68 to rigidly secure the spring arm to the anchor plate. Intermediate the movable main switch contact 54 and the anchor plate '70, the spring arm 68 carries an insulator 74 which is generally channel shaped and has a central shank portion 76 which extends through an opening in the arm 68 and receives a push-n clip 78. This insulator 74 is disposed as illustrated in FIGURE 2 so that the insulator 74 rides upon the follower 48 and prevents direct engagement of the follower 48 with the spring arm 68. It will now be appreciated that upon rotation of the arbor 22, by means of the knob 24, in a counter-clockwise direction as viewed in FIGURE 2, the cam plate 3 4 which rotates with the arbor 22, will move relative to the latch plate 38 until the projection 42 engages the latch plate at the opposite or counterclockwise end of the arcuate slot 48 and thereafter the latch plate 38 will move with the cam plate 34. During this movement, the clockwise side of the notch 44 in the cam plate engages the follower 48 and moves it radially outwardly relative to the arbor 22. It will be noted that the height or radial dimension of the cam. plate 34 is slightly less than that of the latch plate 38 and accordingly, the final lifting of the follower 48 is completed by the engagement of the inclined surface 80 at the outer limit of the clockwise side of the latch plate notch 46. Upon continued rotation of the arbor 22 and the plates 34 and 38, the follower 48 rides on the periphery of the latch plate 38. During this raising, or radially outward movement of the follower 48, it will be appreciated that the follower 48, through its engagement with the insulator 74, on the arm 68, moves the arm 68 to move the movable main contact 54 into engagement with the stationary main contact 52.

The stationary overload contact 56 is mounted on a contact plate 82 which is in turn mounted in the casing 28 in a recess 84, as illustrated in FIGURE 7. The contact plate 82 is electrically connected to the anchor plate 70 by a wire 86, one end of which is secured as by welding to the contact plate 82, and the other end of which is welded or otherwise suitably secured to a laterally extending flange 88 of the anchor plate 70. The movable overload contact 58 is mounted adjacent the free outer end of a bimetal arm 98, the other end of which is secured to a terminal strip 92 provided with a pair of projections 94 extending through apertures in the arm 96 and suitably staked against the remote surface of the arm 90. The strip 92 is mounted in the casing 28 in a recess 96 provided therein, as best illustrated in FIGURE 3.

The strip 92 extends outwardly of the casing 28 through an opening 98 and has an outer terminal portion 180 employed in connecting the mechanism into the electric circuit to be controlled.

Outwardly of the movable overload contact 58, the end portion of the bimetal arm 90 is turned at right angles as indicated at 102 and apertured to receive the outwardly turned end portion 104 of one leg of a U-shaped bimetal snap spring 106, the other leg of which has an outwardly turned end portion 108 which is received in a notch 11() formed in the wall of the casing 28. The laminatio'ns of the bimetal arm 90 are so disposed that heating of the bimetal 90 causes it to warp in a direction to move the movable overload contact 58 away from the stationary overload contact 56. The snap acting bimetal spring 106 applies a force opposing such movement of the bimetal arm 90. When the force de veloped within the bimetal arm 90, as a result of the heating thereof, is suflicient to overcome the force of the snap acting spring 106, the outer end of the arm snaps to the left as viewed in FIGURE 2, moving the movable overload contact 58 away from the stationary overload contact 56 with a snap action and moving the point of engagement of the snap spring portion 104 with the end portion 102 of the bimetal 90 across a line between the engagement of the snap spring end 108 in the notch 110 and the fixed end of the arm 90 which is secured to the terminal strip 92.

Intermediate the movable main switch contact 54 and the movable overload contact 58, is a reset rod 112 formed of a suitable insulating material which is mounted in spaced, aligned grooves 114 and 116 formed in bosses 118 and 128 which are an integral part of the casing 28. The boss 118 has an end portion indicated at 122 which is engaged by the bimetal arm 90 to limit movement of the arm when it snaps to its tripped position in which the movable overload contact 58 is moved away from the stationary overload contact 56. Also, the boss on the casing 28 has a portion indicated at 124 which provides an abutment limiting movement of the spring arm 68 in a direction to move the movable main switch contact 54 away from the stationary main switch con-tact 52. The length of the reset rod 112 is such that when the movable overload contact 58 is in engagement with the stationary overload contact 56, and the arm 68 is against the abutment 124, the distance between the movable main switch contact 54 and the movable overload contact 58 is slightly greater than the length of the rod 112.

The amount of movement of the movable overload contact 58 is such that when the movable main switch contact 54 is in engagement with the stationary main switch contact 52, and the bimetal arm. 90 carrying the movable overload contact 58 is in engagement with the abutment 122, the distance between the movable contacts and 58 is slightly greater than the length of the reset rod 112. Similarly, when the movable overload contact 58 is in engagement with the stationary overload contact 56 and the spring arm 68 carrying the movable main switch contact 54 is in engagement with the abutment 124, the distance between the movable main switch contact 54 and the movable overload cont-act 58 is slightly greater than the length of the reset rod 112. It will now be appreciated that upon rotation of the arbor 22 in a counterclockwise direction from the zero position illustrated in FIGURE 2, the follower 48 will be raised or moved radially outwardly as above described, moving the movable main contact 54 into engagement with the stationary main contact 52. The terminal 66 is then connected to the terminal 100 through a circuit including the stationary main contact strip 68, the main stationary contact 52, the movable main contact 54, the spring arm 68, the anchor plate 70, the wire 86, the overload stationary contact plate 82, the stationary overload contact 56, the movable overload contact 58, the bimetal movable overload contact arm 90, and the terminal strip 92. It will thus be seen that the main contacts 52 and 54 are connected in series with the overload contacts 56 and 58. In the event that a predetermined overload condition occurs, the bimetal 90 will be warped by a force suflicient to overcome the snap spring 106 and snap the outer end of the bimetal arm 90 to the left as above described, and thereby open the circuit by moving the movable overload contact 58 out of engagement with the stationary overload contact 36. During this movement the reset rod 112, if it has up to this time remained in the position illustrated in FIGURE 2, is moved to the left by the engagement of the movable overload contact 53 with the righthand end of the rod. This movement of the rod is permitted because of the fact that the movable main contact 54 has previously been moved to the left from. the position illustrated in FIGURE 2 and into engagement with the stationary main contact 52. As pointed out above, after the overload mechanism has tripped and the bimetal arm 90 is engaging the abutment 122, the distance between the movable contacts 54 and 58 is only slightly greater than the length of the reset rod 112. At the expiration of the time interval for which the timer mechanism has been set by rotation of the arbor 22, the follower 48 drops into the notches 44 and 46 in the cam plate 34 and latch plate 38, permitting the spring arm 68 to move to the right to the position illustrated in FIGURE 2, during which movement the reset rod 112 is forced to the right to the position illustrated and forces the movable overload contact 58 and the bi-metal overload arm 99, upon which it is carried, over center causing the overload mechanism to be reset by snapping the arm 96 to the position illustrated in which the movable overload contact 58 engages the stationary overload contact 56.

FIGURE 9 illustrates the relative position of the parts when the arbor 22 has been turned counterclockwise from the position illustrated in FIGURE 2, to a position in which the timer has been set for a selected time interval. Upon release of the knob 24, operation of the timer mechanism will be initiated and during the initial movement of the arbor 22 by the timer mechanism in a clockwise direction, the latch plate 38 will remain stationary and the cam plate 34 will turn with the arbor until the finger '42 engages the latch plate 38 at the opposite or clockwise end of the arcuate slot 40. Thereafter, the latch plate 38 will turn with the arbor 2.2 and the cam plate 34.

FIGURE 10 shows the overload arm fit) in its tripped position with the movable overload contact 58 out of engagement with the stationary overload contact 56. Upon continued clockwise rotation of the arbor 22 from the position illustrated in FIGURE 10, the inclined cam surface 80 on the latch plate 38, moves under the follower 48 causing the latch plate 38 to quickly advance relative to the arbor 22 and the cam plate 34. This is permitted because of the lost motion connection between the latch plate 38 and the cam plate 34. This results in a quick opening movement of the movable main contact 54 and during this movement the reset rod 112 is pushed to the right, causing the bimetal overload arm 90 to be snapped to the right to the position illustrated in FIG URE 2.

As indicated at the outset of the specification, it is a feature of this invention that the arbor 22 may be manually turned beyond the zero position in the direction in which it is driven by the timer mechanism to close the main contacts without initiating operation of the timer mechanism to return the arbor to ts Zero position. FIG- URE 11 illustrates the position assumed by the parts when this has been done. Upon rotation of the arbor 22 in a clockwise direction from the zero position illustrated in FIGURE 2, the follower 48 is raised or moved radially outwardly by the counterclockwise edges of the notches 44 and 46 in the cam plate 34 and the latch plate 33, respectively.

The latch plate 38 is provided with a radially outwardly extending stop portion 126 spaced counterclockwise relative to the notch 46 to provide a small circular periphery portion 128 between the notch 46 in the latch plate 33 and the stop projection 126. It will now be seen that the arbor '22 and the cam plate 34 and the latch plate 38 may be manually rotated clockwise, from the position illustrated in FIGURE 2, to the position illustrated in FIG- URE 11, in which the stop projection 126 engages the follower 48 and prevents further movement of the arbor 22, and in which the follower 48 being raised, the main switch contacts 52 and 54 are closed. The parts will remain in the position illustrated in FIGURE 11 until the knob 24 is turned to rotate the arbor 22 in a counterclockwise direction sufficiently to move the cam plate 34 and the latch plate 38 to align the notches 44 and 46 thereof with the follower 48, at which time the main contact 54 will be opened with the same snap action described above as occurring at the end of a selected time interval.

The only exception to this is that should an overload condition occur while the parts are in the position illustrated in FIGURE 11, the overload bimetal will snap to its tripped position and move the movable overload contact 58 out of engagement with the stationary overload contact 56 and thus open the circuit.

FIGURES 12 through 18, inclusive, show one modified form of circuit controlling mechanism which may be employed if desired. The construction there illustrated differs from that described above in the following respects. The latch plate 38 is fixed on the arbor 22' and in place of the cam plate 34 fixed on the arbor, there are employed a pair of flipper elements 34' and 34 which are pivotally mounted on the latch plate 38' by pins 35. These flipper elements 34' and 34" are movable relative to the latch plate 38 within limits determined by pins 37 which project into and are movable along slots 39 provided in the latch plate 38'. These flipper elements 34 and 34" are yieldably urged to the positions illustrated in FIGURES 12, 13, l4, l6, l7 and 18 by springs 41 which are best illustrated in FIGURES l3 and 14. As is clearly illustrated in FIGURE 14, one end of each spring engages one of the pins 37 and its other end engages the latch plate 38' at one end Of the slot 39.

FIGURE 12 shows the follower finger 48' in the tripped position corresponding to the position of the follower 48 illustrated in FIGURE 2. When the arbor 22 is rotated in a setting or counterclockwise direction, as viewed in FIGURE 12, the flipper element 34 moves to the position illustrated in FIGURE 15, permitting the cam surface at the clockwise side of the notch in the latch plate 38 to cam the follower finger 48 radially outwardly. Con tinned counterclockwise rotation brings the parts to a set position such, for example, as that illustrated in FIGURE 16, in which the follower finger 48' is supported on the periphery of the latch plate 38. Upon return of the arbor 22 under the influence of the timing mechanism, the latch plate moves clockwise and eventually reaches the position illustrated in FIGURE 17, in which the follower finger 48 is supported on the outer edge of the flipper element 34'. Upon continued clockwise rotation beyond the position illustrated in FIGURE 17, the follower finger 48' drops between the flipper elements 34' and 34", the former moving, as required, against the action of its spring 41 to provide a snap opening of the main contacts.

FIGURE 18 illustrates a continuous operation position similar to that illustrated in FIGURE 11 and in which the timing mechanism cannot drive the arbor 22'. In turning the arbor 22' clockwise beyond the Zero position illustrated in FIGURE 12, to reach the position illustrated in FIGURE 18, the flipper element 34" pivots counterclockwise relative to the latch plate 38 to permit the cam surface at the counterclockwise side of the notch in the latch plate 38' to cam the follower finger 48' radially outwardly. Rotation of the arbor 22 and latch plate 38, clockwise, beyond the position illustrated in FIGURE 18, either manually or by the timing mechanism, is positively prevented by the engagement of the projection 126' on the latch plate 38 with the follower finger 48'. Upon manually returning the arbor 22 to the zero position illustrated in FIGURE 12, it will be appreciated that the flipper element 34" provides a snap action of the follower 4S and the main contacts controlled thereby.

While several embodiments of the invention have been illustrated and described in detail herein, it will be readily appreciated by those skilled in the art that numerous modifications and changes may be made without departing from the spirit of the invention.

What is claimed is:

1. Means for controlling the current in an electric cirouit comprising a normally open main switch, timer mechanism settable for a selected desired period and effective 5 upon setting thereof to close said switch and hold said switch closed for said selected period, resettable overload switch mechanism for automatically opening said circuit upon the occurrence of a predetermined overload condition in said circuit, and reset mechanism automatically operated at the end of said selected period for resetting said overload switch mechanism.

2. Means for controlling the current in an electric circuit comprising manually operable means including main contacts for closing and opening said circuit, resettable overload means including overload contacts in series with said main contacts, said overload means operating automatically upon the occurrence of a predetermined overload condition in said circuit to open said overload contacts, and mechanical resetting means automatically resetting said overload means upon operation of said first named means to open said circuit and including a reset element engaged by said first named means during said operation thereof and engageable with said overload means during operation of said first named means to open said circuit to close said overload contacts.

3. Means for controlling the current in an electric circuit comprising conditionable means for automatically openin said circuit, manual means for closing said circuit and conditioning said conditionable means to automatically open said circuit at the expiration of a predetermined desired interval after the manual closing of said circuit, resettable overload means for automatically opening said circuit upon the occurrence of a predetermined overload in said circuit, and means for automatically resetting said overload means after the expiration of said predetermined desired interval from said manual closing of said circuit in response to operation of said conditionable means to open said circuit.

4. Means for controlling the current in an electrical circuit comprising a timer, a main switch, a timer controlled main switch mechanism manually operable to close said main switch and set said timer for a predetermined period and automatically operated at the end of said predetermined period to open said main switch; an overload switch mechanism operated by a predetermined overload in said circuit to trip to an open condition; and a reset element movable to reset said overload switch mechanism to closed condition; said main switch mechanism, upon automatic operation to open said main switch after operation of said overload mechanism in response to an overload, moving said reset element to reset said overload switch mechanism.

5. Means for controlling the current in an electrical circuit as defined in claim 1, wherein said main switch mechanism includes a pair of main switch contacts and said overload switch mechanism includes a pair of overload contacts connected in series with said main switch contacts.

6. Means for controlling the current in an electrical circuit as defined in claim 4, wherein said main switch mechanism includes a stationary main switch contact, a movable main switch contact, and a main switch arm carrying said movable contact, said overload switch mechanism includes a stationary overload contact and a movable overload contact, and said reset element is disposed between said main switch arm and said movable overload contact.

7. Means for controlling the current in an electrical circuit as defined in claim 4, wherein said main switch mechanism includes a stationary main switch contact, a movable main switch contact, and a main switch arm carrying said movable contact, said overload switch mechanism includes a stationary overload contact, a movable overload contact, and means for tripping said overload switch mechanism to move said movable overload contact out of engagement with said stationary overload contact, and said reset element is disposed between said main switch arm and said movable overload contact, said main switch arm being moved as a part of said automatic operation of said main switch mechanism and after operation of said overload switch mechanism to move said reset element to move said movable overload contact into engagement with said stationary overload contact.

8. Means for controlling the current in an electric circuit, said means comprising a pair of main contacts operable for closing and opening said circuit, actuating means operable in one manner to close said main contacts and in a second manner to open said main contacts, a pair of overload contacts, overload means operable upon a predetermined overload in said circuit to operate said overload contacts and open said circuit, and mechanical reset-ting means operable after operation of said overload means to automatically reset said overload contacts, said actuating means when operated in said second manner and after operation of said overload means being efifective to engage and operate said resetting means to reset said overload contacts.

9. Means for controlling the current in an electrical circuit as defined in claim 8, wherein said actuating means for operating said main contacts includes a main switch arm movable in one direction to close said main contacts and movable in the opposite direction to open said main contacts, said main switch arm, upon movement in said opposite direction after operation of said overload means, engaging and operating said resetting means.

10. Means for controlling the current in an electrical circuit comprising a pair of main contacts adapted to be connected in series in said circuit, a pair of overload contacts connected in series with said main contacts, mtan ual means for closing said main contacts, means for automatically opening said main contacts after the expiration of a predetermined desired interval, means for opening said overload contacts upon the occurrence of predetermined overload conditions in said circuit, a movable reset element disposed adjacent said main contacts and said overload contacts and operated, in response to opening of said main contacts when said overload contacts are open, to close said overload contacts.

11. Means for controlling the current in an electric circuit as defined in claim 10, wherein each of said pairs of contacts includes a movable contact, and said reset element is moved by engagement with said movable contacts.

12. Means for controlling the current in an electric circuit as defined in claim 10, including a casing, and wherein each of said pairs of contacts are mounted in said casing with the adjacent contacts of said pairs of contacts movably mounted, and wherein said reset element is mounted in said casing for free movement relative thereto and is moved by engagement with said movably mounted contacts.

13. Means for controlling the current in an electric circuit as defined in claim 10 including a casing, and wherein each of said pairs of contacts are mounted in said casing with the adjacent contacts of said pairs of contacts movably mounted, and wherein said reset element is a rod mounted in said casing between said movably mounted contacts for free movement relative to said casing and longitudinally of said rod and said rod is moved by said movably mounted contacts engaging its ends.

14. Means for controlling the current in an electric circuit comprising a pair of main contacts for closing and opening said circuit, a timer having an arbor turnable in one direction from a zero position for initiating operation of said timer and means yieldably urging said arbor in the opposite direction, cam means on said arbor, means including a follower co-operating with said cam means and effective to close said circuit upon a predetermined movement of said arbor in said one direction from said Zero position and effective to open said circuit upon said arbor returning to said zero position, said cam means including a stop engageable with said follower for limiting movement of said arbor in said opposite direction, said cam means and said means including a follower being effective upon movement of said arbor in said opposite direction beyond said zero position to close said circuit and move said stop into engagement with said follower to prevent further movement of said arbor in said opposite direction.

15. Means for controlling the current in an electric circuit comprising a pair of normally open contacts, a timer having an arbor turnable in one direction from a zero position for initiating operation of said timer and means biasing said arbor in the opposite direction under the control of a timing mechanism, cam means on said arbor, means including a follower co-operable with said cam means to close said contacts, said cam means and said follower oo-operating upon movement of said arbor in either direction from said zero position to move said follower and through said means including said follower to close said contacts, and stop means on said cam means disposed to engage said follower and limit movement of said arbor in said opposite direction.

16. Means for controlling the current in an electric circuit comprising a stationary contact, a movable contact movable into and out of engagement with said stationary contact for closing and opening said circuit, said movable contact being biased away from said stationary contact, a timer having an arbor rotatable in one direction from a zero position for initiating operation of said timer and means biasing said arbor in the opposite direction under the control of a timing mechanism, a cam element fixed on said arbor for rotation therewith, a latch plate having a lost motion connection with said cam element, a follower co-operating with said cam element and latch plate upon rotation of said arbor in said one direction from said zero position to move said movable contact into and hold it in engagement with said stationary contact, said follower also co-operating with said cam element and said latch plate upon rotation of said arbor in said opposite direction from said zero position 10 to move said movable contact into and hold it in engagement with said stationary contact, and stop means on said latch plate which engages said follower to limit rotation of said arbor from said zero position in said opposite direction.

17. The combination defined in claim 15 including means on said cam means and co-operable with said follower to provide a snap opening of said contacts whenever said arbor is returned to said zero position.

18. The combination defined in claim 15 wherein said cam means includes a cam disc having a notch in its periphery, and including a pair of elements pivotally mounted on said disc at opposite sides of said notch and each movable to a position in which it overlies a portion of said notch and adapted to support said follower when said follower overlies said portion of said notch during return of said arbor to said zero position.

References Cited in the file of this patent UNITED STATES PATENTS 1,424,003 Connely July 25, 1922 1,935,371 Osborne Nov. 14, 1933 2,106,269 Brosseau Jan. 25, 1938 2,446,474 Harrold Aug. 3, 1948 2,582,027 Goff Jan. 8, 1952 2,685,636 Vogelsberg Aug. 3, 1954 2,911,501 Baker Nov. 3, 1959 FOREIGN PATENTS 618,921 Great Britain Mar. 1, 1949 

